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ANNUAL INDUSTRY WORKSHOP NOVEMBER 12-13, 2014 Robust GPS-Based Timing for Phasor Measurement Units A Position-Information-Aided Vector Tracking Approach NOVEMBER 12, 2014 DANIEL CHOU UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN TRUSTWORTHY

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ANNUAL INDUSTRY WORKSHOP NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.ORG

UNIVERSITY OF ILLINOIS | DARTMOUTH COLLEGE | UC DAVIS | WASHINGTON STATE UNIVERSITY

FUNDING SUPPORTPROVIDED BY DOE-OE AND DHS S&T

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Robust GPS-Based Timing for Phasor Measurement Units

A Position-Information-Aided Vector Tracking Approach

DANIEL CHOU

UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN NOVEMBER 12, 2014

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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

GPS Basics

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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

Phasor Measurement Units (PMU)

  • Measures electrical waves to improve stability in power grids.
  • Observation frequency:

– SCADA: 1 sample every 4 seconds. – PMU: 30-60 samples/sec.

  • Measurements time-stamped using GPS clock readings.
  • Measurement information can be used to fine-tune the power grid to

improve efficiency and detect instability and disturbances.

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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

Motivation

  • GPS robustness and reliability directly influences PMUs.
  • GPS receivers are vulnerable to:

– Frequency leakage from radio signals – Interfering electromagnetic fields – Accidental jamming – Spoofing attacks Goals:

  • Robustness against interference
  • Spoofing detection
  • Accurate timing solutions

http://www.nj.com/news/index.ssf/2013/08/man_fined_32000_for_blo cking_newark_airport_tracking_system.html

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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

Outline

  • Position-Information-Aided Vector Tracking

– Approach – Implementation

  • Experimental Results

– Hardware – Tracking results

  • Conclusions
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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

Outline

  • Position-Information-Aided Vector Tracking

– Approach – Implementation

  • Experimental Results

– Hardware – Tracking results

  • Conclusions
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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

Approach: Position-Information-Aided (P.I.A.) Vector Tracking

Approach:

  • Vector tracking
  • Reduces the search space

– Aided by the true position

  • Kalman filtering

– Recursively predict and update the errors

  • Narrowband loop filter
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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

Scalar Tracking

GPS Front-end Correlator Code and Carrier Discriminators Navigation Processing Incoming Signal NCO Channel 1-N 𝑔

𝑒,

𝜚 Position and Time Solutions (𝑦, 𝑧, 𝑨, 𝑢)

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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

Implementation: P.I.A. Vector Tracking

GPS Front-end Correlator Code and Carrier Discriminators Incoming Signal Known True Position (𝑦, 𝑧, 𝑨) NCO Timing Errors Channel 1-N 𝑔

𝑒,

𝜚 Time Solution (𝑢)

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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

Outline

  • Position-Information-Aided Vector Tracking

– Approach – Implementation

  • Experimental Results

– Hardware – Tracking results

  • Conclusions
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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

GPS Front End

Receiver

  • SiGe Sampler

– 2 bit quantization – Bandwidth: 2.72MHz – Low-cost, off-the-shelf Antenna

  • Novatel Antenna

– Fixed-reference antenna – Choke ring form

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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

P.I.A. Vector Tracking Improves Accuracy

  • Loop filter bandwidth of

5Hz for both scalar and P.I.A tracking loops.

  • 9 satellites in view

Maximum errors:

  • Traditional tracking

– ~50ns

  • Proposed vector tracking

– ~15ns

No Noise Added

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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

P.I.A. Tracking Increases Noise Tolerance

  • Increased noise leads to loss of lock in

scalar tracking.

  • At 4 dB of additional noise, the scalar

tracking was able to produce navigation bits for 4 satellites.

1 dB Noise Added 4 dB Noise Added

Noise Added # of Satellites Tracked in Scalar 0 dB 9 1 dB 8 3 dB 5 4 dB 4

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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

P.I.A. Tracking is Robust Against Jamming

  • Scalar tracking fails at 5 dB of added noise.
  • P.I.A. Vector Tracking continued to operate up until 9 dB of

additional noise (5 dB more noise tolerance over scalar tracking)

  • Reduces a jammer’s effective radius.

5 dB Noise Added 9 dB Noise Added

Scalar tracking fails P.I.A. still tracking Scalar tracking fails P.I.A. still tracking

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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

P.I.A. Tracking Detects Meaconing

  • Meaconing: record and

replay legitimate GPS signal.

  • Meaconing attack

simulated.

  • P.I.A. Vector Tracking

loop fails to converge in the event of a meaconing attack.

  • 200 meter difference in

known position and meaconing position.

Meaconing attack begins

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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

Outline

  • Position-Information-Aided Vector Tracking

– Approach – Implementation

  • Experimental Results

– Data Collection – Results

  • Conclusions
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ANNUAL INDUSTRY WORKSHOP – NOVEMBER 12-13, 2014

TRUSTWORTHY CYBER INFRASTRUCTURE FOR THE POWER GRID | TCIPG.OR G

Conclusions

  • Proposed the Position-Information-Aided Vector Tracking approach

for GPS-based timing.

  • Conducted experiments to evaluate the performance of the

proposed approach.

  • Validated:

– Robust against jamming (5dB more noise tolerance compared with scalar tracking); – Successfully detects meaconing attacks; – Improves the accuracy of the timing solutions (15 ns vs 50 ns).